In order to make aircraft passengers comfortable, and in order to transport them between an airport terminal building and an aircraft in such a way that they are protected from the weather and from other environmental influences, passenger boarding bridges are used which are telescopically extensible and the height of which is adjustable. For instance, an apron drive bridge in present day use includes a plurality of adjustable modules, including: a rotunda, a telescopic tunnel, a bubble section, a cab, and elevating columns with wheel carriage. Other common types of passenger boarding bridges include radial drive bridges and over-the-wing (OTW) bridges. These types of passenger boarding bridges are adjustable, for instance to compensate for different sized aircraft and to compensate for imprecise parking of aircraft at an airport terminal.
A manual bridge alignment system requires that a human operator is present to perform the alignment operation each time an aircraft arrives. Delays occur when the human operator is not standing-by to perform the alignment operation as soon as the aircraft comes to a stop. In addition, human operators are prone to errors that result in the passenger boarding bridge being driven into the aircraft or into a piece of ground service equipment. Such collisions involving the passenger boarding bridge are costly and also result in delays. In order to avoid causing a collision, human operators tend to err on the side of caution and drive the passenger boarding bridge slowly and cautiously.
Semi-automated bridge alignment systems also require a human operator, but the human operator may be present at a remote location and interact with the bridge control system in a tele-robotic manner. One human operator may interact with a plurality of different passenger boarding bridges, thereby reducing the costs associated with training and paying the salaries of human operators. Alternatively, certain movements of the bridge are automated, whilst other movements are performed under the control of the human operator.
Automated bridge alignment systems provide a number of advantages compared to manual and semi-automated systems. For instance, automated bridge alignment systems do not require a human operator, and therefore the costs that are associated with training and paying the salaries of human operators are reduced or eliminated. Furthermore, an automated bridge alignment system is always standing by to control the passenger boarding bridge as soon as an aircraft comes to a stop. Accordingly, delays associated with dispatching a human operator to perform a bridge alignment operation are eliminated, particularly during periods of heavy aircraft traffic.
Early attempts at automated bridge alignment systems employed imagers and sensors disposed on or about the passenger boarding bridge, for sensing locations of aircraft doorways and for sensing close approach of the bridge to the aircraft. More recently, automated bridge alignment systems have been developed in which beacon docking signals and/or control signals are transmitted wirelessly between an aircraft and a passenger boarding bridge, as described for example in U.S. Pat. Nos. 6,637,063, 6,742,210, 6,757,927 and 6,907,635, the entire contents of all of which are incorporated herein by reference. Other systems relying upon wireless transmission of signals between an aircraft and a passenger boarding bridge during alignment are disclosed in U.S. patent applications Ser. Nos. 11/149,401, 11/155,502, 11/157,934 and 11/157,938, the entire contents of all of which are incorporated herein by reference. Unfortunately, automated bridge alignment systems still are prone to errors that result in the passenger boarding bridge being driven into the aircraft.